Tube bending



2 Sheets-Sheet l H. J. STEEL TUBE BENDING April 5, 1966 JNVENTOR. Hofmse J. STEEL LM, MVM

AroeA/Eys April 5 1966 H. J. sTEE-L 3,243,873

TUBE BENDING Original Filed Dec. 6, 1961 2 Sheets-Sheet 2 JNVENToR. Howe-e J 575-54 A frog/VE v5 United States Patent O 3,243,873 TUBE BENDING Homer J. Steel, 925 Madera Circle,

Elm Grove, Wis.

P.O. Box 392,

Continuation of application Ser. No. 157,520, Dec. 6, 1961. This application Apr. 26, 1965, Ser. No. 463,415 41 Claims. (Cl. 29-157) bend radius wall. the 'interior or exterior surfaces of the above should be avoided, as well as general requirements and the A.S.T.M. specification for welding fittings.

Generally in accordance with ing and holding the latter. The trailing portion of said free mandrel is disposed within and supports the leading end of a following workpiece. In accordance with another aspect of the invention, and in another emboditact with the die until the elbow is formed.

The structure may include a plunger associated with provide a very rigid structure when assembled in a suitable frame. In each case, two traveling mandrels act in shaping the walls of a pipe to conform to the curvature of the forming passage. In each case, one mandrel is ixed to a plunger for applying pressure to the end face of the pipe. In one embodiment, the other mandrel is FI `bodiment of 3,243,872 Patented Apr. 5, 196i other mandrel connected with a nally but curved transversely, that is cylindrical, so that the mandrel comes nearly to points at the ends and provides compound curved lower surface portions.

In the drawings:

GURE l is a vertical cross sectional view of one ema preceding workpiece;

FIG. 2 is a perspective view of the sleeve which is attachable to the press plunger yfor exerting force on the workpiece; y

FIG. 3 is a fragment of FIGURE 1 showing the interaction of one -workplece and the forming surfaces acting thereon at the end of a pressure plunger stroke;

of two -workpieces in the machine at a time intermediate loading and discharge of the devices;

FIG. 5 is an elevation of a Ibi-ank showing the initial shape yof the ends thereof;

FIG. 6 is an elevation of a from the blank 'of FIG. 5;

FIG. 7 is an elevation showing the workpiece of FIG. 6, trim-med to length and |beveled to form an elbow for welding in place Ibetween two lengths of piping;

FIG. 8 is a side elevation of one-half of a stationary die structure which may be substituted yfor the other die members in the machine of FIGS. l-4;

IFIG. 9 is ia front elevation of the complete die of FIG. i8;

FIG. 10 is a plan view of the forming roller and showing the die groove, and the elongated bearing portions of the roller;

FIG. 11 is a View 'bent workpiece formed partially -in section and partially of the present when .the workpiece is partially formed; and

FIG. 13 Iis a lfragmental view similar to FIG. 11, but showing the machine parts and a workpiece in' position when the workpiece has 'been :ful-ly formed.

As shown in FIGURE l of the drawings, 'a horizontal :base 1'5 of heavy metal plate has fixed :thereto a heavy -metal vertical frame 16 which is substantially U-'shaped in plan and which has an aperture through the Iframe. Rotatable yforming means, such as a roller 17 is disposed with the ends thereof `supported on a number of roller lbearings 18 in the trame 16, only one Ibearing being shown. The portion of roller 17 inside the space dened by the frame, is shaped to provide a die groove -f the size and of -inner radius corresponding to the inier curved surface of the fittings to be formed thereby. n dimensioning the groove in roller i17, the radius of he groove should confor-rn to the inner surface radius lesired for a workpiece of a particular siz A gen- :rally L-shaped and grooved die member or support 22 is seated in iixed position in uframe 16 between a vertical backplate 23 and a ybottom plate 24. Thus support 22 can be'easily brought into position around roller 17 so that some ofthe edges of the groove of support 22 conform to the edges of the groove'in the roller.

A vertical guide block 25 is formed with a die groove complementing the groove in fixed support 22 its edges mating with some of the edges of 'support 22 so that a passage of desired size-is provided. The lowervedge of guide ib'lock 25 conforms to the surface of roller 17 and the groove therein coacts with the lgroove in support 22 to define the entrance to lthe for-ming passage through which the workpieces are pressed. The guide Iblock 25 is held in place by a screw 29 threaded into a cross piece removably seated in notches in the legs of frame 16 and extending across the space therein.

A horizontal former plate 31 forms an extension of `the lower portion yof support 22 yand is held in place against the Ksupport 'by a screw 32 threaded into cross piece 33 which is also held in notchesin frame 16 and extends across the recess in such frame. Former plate 31 is to provide a continuation of the groove in support 2.2. The groove in support 22 and continuing into former pla-te 31 is shaped toa diameter tto produce `the desired outer radii of the pipe bend.

As shown in FIG. 5, the hollow pipe blanks to be shaped .into elbows and bends are cut into short pieces 34 so that the outer radius of the finished piece is formed from portion 35, and the inner radius thereof-is formed from portion 36. Thus, additional `metal is provided where the workpiece wall tends to lengthen. The leading end of the workpiece which enters the forming passage is lirregular and cut at a right angle to the workpieces longitudinal centerline, as at flat portion 37, while the adjacent end portion E38 is cut at an acute angle to the said centerline. The trailing end of the workpiece is also irregular and cut at a rig-ht angle to the longitudinal centerline as -at flat portion 39, and is cut at an acute angle to the longitudinal line as at 40. This second angle is much smaller than the first angle. After final forming, and as shown in FIG. 7, the elbows are cut to the length specified and the ends are beveled as at 41 for welding to similarly beveled ends of-pipirig.

For purposes of pipe forming, an elongated solid, rigid traveling imandrel 46 is provided which is completely free from any machine parts. Mandrel 46 'has an annular yseat or rim-like Icollar 47 rformed midway of the length thereof. As shown in FIGS. l, 3 `and 4, the inner surface portion 48 of mandrel 46 is straight longitudinally but curved transversely while the outer surface thereof is curved both longitudinally and transversely to provide continuous compound curved trailing outer surface 49 and leading outer surface 50. The mandrel is thus generally 'banana-shaped with generally pointed ends. The inner leading end port-ion of the mandrel is shaped as shown at 51 to facilitate entrance into the preceding workpiece.

As shown in FIGS. 1 4, free mandrel 46 is adapted to cooperate with and assist in forming two workpieces in succession. During forming, the leading end of the mandrel is adapted to enter and be enclosed within the trailing end of a preceding workpiece, while the trailing end of the mandrel is adapted to enter and be disposed within the leading end of a following workpiece, and acting as a cantilever in support of the wall.

The inner surface 4S of the mandrel conforms to the bore of the workpiece and the outer surfaces 49, Sil of ing end of mandrel 46 will rock so the mandrel conform severally to the outer wall of the workpiece as the mandrel moves about the roller.

The workpieces are pressed in succession in a curved path, that shown being circular, by a sub-assembly including a plunger 55 formed at its pressing or leading end 56 in the banana-like shape of the leading portion of mandrel 46. Plunger end 56 is fixedly mounted in a sleeve 57 which is shown in FIGS. 2 and 3 in enlarged The leading outer portion of the sleeve end is irback, to form a step 58, and is transverse to the sleeve centerline to thus make two sharp corners with intermediate forwardly extending tooth portions V59 of the sleeve, while the inner portion of the sleeve end forms a slightly cut back angular portion 60.

Prior to the first complete forming operation, a scrap workpiece is inserted into `the forming passage and plunger 55 is moved downwardly. The scrap workpiece is thus forced downwardly and partially through the passage. Plungei- 55 is then withdrawn and a free mandrel 46 is inserted into the passage so that the heading mandrel end is disposed within the trailing end of the scrap workpiece and mandrel collar 47 bears on the workpieces trailing end. This scrap workpiece assumes the position that all later-formed workpieces do, the numeral 34a in FIGURE 1 of the drawings designating either the scrap workpiece or a subsequent workpiece in the same position.

A second workpiece with its forward end over the trailing end of mandrel 46, and the press plunger 55 is again brought to bear on the trailing end of workpiece 3417 and xedly moves therewith.

Plunger 55 again moves downwardly and the step 58 thereof contacts the flat trailing end portion 39 of Vworkpiece 3415. As workpiece 34b begins to move around the bend, the metal flows so that the toothed portion 59 of ,the sleeve end digs into the workpiece end and Vprogressively seats on some of the surface 40 of the workpiece. The inner portion of surface 40 is free to expand longitudinaily and toward sleeve 57. (See FIG. 3.) Mandrel 56 and workpiece 34h move together at all times, no substantial relative axial movement occurring therebetween.

As the bend in the forming passage is reached, the trailthat its trailing outer surface 49 progressively contacts and supports the outer wall of workpiece 34h and presses it into the forming groove. (Compare FIGS. l and 3.) This will support the outer wall fibers of the leading half of workpiece 34b against flattening in a rearwardly progressing manner from the forward end thereof toward the workpiece midportion. At the same time, inner surface 48 of mandrel 46 will support the inner wall fibers from collapse at the leading end of workpiece 34b in line contact continuously during formation of the bend.

The free mandrel and the outer wall of workpiece -34b remain fixed relative to each other during the bending operation,with substantially no relative axial movement occurring. Both move only arcuately.

The outer wall of the second workpiece 34h will-tend to stretch in tension during the bending operation. (See FIG. 4.) However, rim 47 of the mandrel will put lengthwise compression on the outer wall of the leading `end of the workpiece, as at flattened portion 37, which adds to the lengthwise compressive forces generated by sliding friction between the outer surface and support Z2. As best seen in FIG. 4, the inner wall of the second workpiece 34h will be unconned longitudinally and may shorten slightly. The major amount of plastic ow will be along the neutral axis extending generally intermediate the inner and outer surfaces with the plane of the ends being readjusted. Both ends of the workpiece will end up generally planular, as shown in FIG. 6.

Throughout bending, he forward end of mandrel46 will rigidly anchor within the trailing end of the inner wall of first workpiece 34a and causes the mandrel as a whole to act as a cantilever inapplying outward oriented forces by the trailing end of the mandrel. In addition,

i are in the position shown in FIG. 1l

the forward end of the mandrel will support the trailing end of the outer wall of workpiece 34a after the aforementioned rocking action has taken place.

When plunger 55 reaches its lowermost position, as in Stainless steel tubing ihas a tenden-cy to gall when subjected to cold bending :and sliding in close frictional contact with another surface. Instead of using an inner forming roller and fixed outer -grooved members, a die made wholly of stationary parts of a suitable then be used as shown in FIGS. 8 and 9. FIG. 8 shows one-half of a stationary former member 'made of ari alloy :having 'high strength and non-.galling properties, aluminum bronze having been found satisfactory. The completed former includes the right hand half 64 and a left by bolts 67. The present modification may be held on a suitable press. rEhe use of -a free traveling mandrel 46 and the sequence of steps is as described for FIGS. 1-4.

-Referring now to FIGS. 11-13, a die member such as 4a moderate resistance to roller movement and can be controlled to position the roller. The block 74 has a socket and hole in which is mounted a portion of a rigidly mountsure plunger 90, with the latter having a banana-like plunger mandrel portion 91 fixed thereto andv a sleeve portion 92 having its end for-med in a manner similar to that of FIGS. 1-4. The plunger 90 is 'rigidly secured to guide 89 by a suitable clamp93. The mandrels 83 and 91 are .captive to their respective mountings and the leading end of the mandrel 91- is cut short to clea-r the end of the mandrel 83 as shown in FIG. 11.

In operation, when block 74 and its captive mandrel 83 and plunger 90 and mandrel 91 are retracted, a workpiece 34 may be loaded to seat on the sleeve 86 and rests in g-rooved die 89. The press pluri-ger sleeve 92 is then moved endwise in a straight and -inove the workpiece against the yieldthe fluid pressure cylinder 77. The force stantial axial or longitudinal movement between the mandrels and the workpiece during bending. The grooved die 89 provides inwardly directed bending pressure in coin cylinder 77 while plunger mandrel 91 is retracted to its initial position. The bent rThe present invention provides for substantially improved tube bending procedures when cold forming is desired. Collapse of the walls is prevented during forming operation, as contrasted with prior procedures wherein collapse occurs and the workpiece -must then be restored. The walls of the yfinished workpiece are substantially uniform throughout.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In a machine for cold forming a length of pipe into a bend:

(a) aframe,

(b) a roller with 'a peripheral groove having a partial cylindrical cross section and rotatably mounted in the frame,

(c) a member on the frame for coacting with the roller in providing a passage for forming a pipe into a bend of given inner and outer radii.

(d) first means for receiving the leading end of a pipe within the forming passage and disposed to travel with the pipe through the forming passage in fixed axial relation to the pipe, said first means being constructed to progressively support the outed wall of the pipe against flattening in the leading half portion thereof during said trave (e) and second means for entering the trailing end of the pipe and disposed to travel in fixed axial relation therewith through a portion of the passage,

(f) said iirst and lsecond means coacting in forming the pipe into the passage radii.

2. The machine of andasse lius Walls and is spaced from the pipe end at the inner ,'adius wall thereof.

3. The machine of claim 1 in which the first means :omprises a leading mandrel having a collar extending outwardly therefrom midway of the mandrel length for simultaneous bearing thereon of an end of two successive pipe lengths.

4. The machine of claim 1 in which the first means comprises a leading mandrel having a collar extending outwardly therefrom midway of the mandrel length for bearing thereon of successive pipe lengths and being of a diameter substantially equal to the diameter of the forming passage for coacting with the leading pipe length in yieldingly resisting axial movement of the following pipe during movement through a portion of the passage.

5. The machine of claim 1 in which the first means comprises a leading mandrel having an external collar midway of its length and the mandrel tapers from the collar toward both mandrel ends for supporting both the inner and outer radius ypipe walls in the leading half portion of the pipe, and the second means comprises a pressure plunger having a forward end similar in shape to the adiacent end of the leading mandrel.

6; In an apparatus for forming elbows from straight tubular blanks,

(a) a die member having a groove therein with a portion curved corresponding to the minimum inner radius of the elbow to be formed,

(b) means to move the blank progressively along said curved groove from an initial position substantially tangential to said curved portion and in contact with said die member until the elbow is formed,

(c) and spaced blank forming means disposed inside the blank at each end thereof and having an outer dimension and configuration corresponding to the inner dimensions of the finished elbow in the portion of maximum radius, the blank forming means disposed at the leading end of the blank being constructed to act as a cantilever to progressively support the outer wall of the pipe against flattening in the leading half portion thereof during movement of thae blank,

(d) said forming means lixedly moving with the balnk during the elbow forming operation.

7. The apparatus of claim 6 which includes: yieldable means for resisting the movement of said blank during travel thereof in said groove.

8. The machine of claim 6 in which said die member comprises a movable forming roller, and a piston under pressure is connected with the roller for yieldingly resisting movement thereof.

9. The machine of claim 8 in which the said blank forming means comprises a leading mandrel and a trailing pressure plunger, said mandrel and said plunger having a sleeve fixed thereon and bearing on the respective pipe ends in xed axial relation to the pipe during movement of the pipe around the roller.

10. In an apparatus for continuously forming elbows from straight tubular blanks,

(a) die means forming a curved passageway for receiving a series of blanks in succession therethrough,

(b) and means to move the said blanks progressively in succession through said passageway, said moving means including a free mandrel disposed within said passageway,

(c) the forward end portion of said mandrel being formed to be disposed within the trailing end portion of a preceding blank for supporting said trailing end portion against collapse,

(d) the rearward end portion of said mandrel being formed to be disposed within the forward end portion of the next succeeding blank for supporting the latter end portion against collapse,

(e) said mandrel xedly moving in said passageway with both said preceding blank and said next succeeding blank during the elbow forming operation.

11. The apparatus of claim 10 in which the mandrel comprises:

(a) an elongated generally banana-shaped member,

(b) the inner surface portion of said mandrel being generally straight longitudinally but curved transversely,

(c) the outer surface portion of said mandrel being curved both longitudinally and transversely to provide continuous compound leading and trailing outer surfaces,

(d) the said mandrel being constructed to rock in said passageway so that the trailing compound outer surface of said mandrel-contacts the outer wall of the leading end portion of the said next succeeding blank progressively from the end of the blank rearwardly toward the midportion thereof to support sbaiddwall against flattening during formation of the 12. The apparatus of elairn 11 in which the said mandrel includes an annular rim disposed centrally thereof for seating the trailing and forward ends of two blanks traveling in succession.

13. For use in an apparatus for forming elbows from straight tubular blanks, a free mandrel comprising:

(a) an elongated generally banana-shaped body adapted to enter and support the walls of adjacent blanks,

(b) the inner surface portion of said body being generally straight longitudinally but curved transversely,

(c) and the -outer surface portion of said body being curved both longitudinally and transversely to provide continuous compound leading and trailing outer surfaces,

(d) and an annular rim disposed centrally body for seating the trailing and forward two blanks to be formed.

14. For use in an apparatus for forming elbows from straight tubular blanks, a mandrel comprising:

(a) a body portion adapted to enter and support the forward end portion of a blank to be formed,

(b) and stop means disposed on said body for seating the forward end of a blank,

(c) said body portion being shaped to support the outer wall `of the blank progressively from the forward end thereof and rearwardly toward the central portion thereof during formation of the elbows.

15. In an apparatus tubular blanks:

(a) means -to move a blank in a curved path,

(b) means to support the rearward end portion of a blank against collapse as it is moved in said path,

(c) and rigid means adapted to be disposed within the leading end portion of a blank, said last-named means 'being shaped to contact and support against attening the outer wall of said leading end portion in a progressive manner from the end of the blank rearwardly toward the central portion thereof during movement of the blank in said path.

16. The apparatus of claim 15 which includes means to support the `leading end lof the inner wall of a blank against collapse continuously during movement of the blank in said curved pa 17. In an apparatus for forming an elbow from a straight tubular blank having an irregular trailing end with an outer flat transverse portion and a tapered inner portion:

(a) means for moving said blank in to form an elbow,

(b) said means including a member for contacting the trailing end of the blank,

(c) said member having a toothed portion which digs into the blank progressively as the metal flows during forming.

of said ends of for forming elbows from straight a curved path 18. In an apparatus for forming elbows from straight tubular blanks:

(a) means to move a lblank in a curved path so that means comprising:

(l) a yfirst member engageable with the trailing end face of said outer wal-l,

(2) and a second member disposed for longitudinal engagement with the forward end face of said outer wall,

(3) both said members lixedly traveling with the blank during forming.

19. The apparatus of claim 18 in which said blank and membersfare constructed'and disposed so that the inner wall of the bl-ank is unconfined longitudinally.

20. In an apparatus for forming elbows from straight tubular blanks:

(a)'a die forming a curved supporting surface for receiving the inner radius wall of a blank,`

(b) a plunger engageable with the outer trailing end face of a blank and with said plunger being movable in a straight path,

(c) a rst mandrel connected to said plunger and disposable Within the said trailing end of the blank for vsupporting the latter,

(d) a mem-ber disposable adjacent the forward end of the vblank and movable arcuately about the center of said curved surface,

' (e) and a second mandrel separate from said first 21; The apparatus of claim 20 which includes: yieldable means `connected to said member for resisting arcuate movement thereof as la blank is being formed around said supporting surface by movement of said plunger.

22. The apparatus of claim which includes: a die member ixed for straight movement with said plunger and having :a groove for supportinglthe trailing end of the blank during forming.

23. In an apparatus forming elbows from straight tubular blanks:

(a) a die forming a curved supporting surface for receiving the inner radius wall of a blank,

(b) a .plunger engageable with the trailing end of a blank and with said plunger being movable in a straight path,

(c) a first mandrel connected to said plunger and disposable within the said trailing end of the blank for supporting the latter,

(d) a member disposable adjacent the forward end of the blank and having a shallow cup therein and movable arcuately about the center of said curved surface,

(e) and a second mandrel rigidly mounted within said cup and thereby spaced from said member,

(f) said second mandrel adapted to receive the forward end of the blank thereover so that said forward end is disposed within said vcup and supported by the wall of said cup, ,saidrsecond mandrel being shaped to progressively contact the outer Wall of the blank from the forward end of the wall rearwardly toward the midportion thereof.

24. In a machine for cold forming a pipe workpiece into a pipe bend, a cylindrical rotary former having an arcuate peripheral groove therein, a pressing mandrel sub-assembly having a portion insertable int-o and a portion pressing endwise on the workpiece and movable in leading mandrel sub-assembly is mounted on and moves in an arc about the rotory former.

and turning the rotary former in the other direction.

30. In a method for forming -lengths of metal pipe into elbows, the steps of cutting the ends of a length of curve of the passage while supporting the outer pipe wall progressively from the forward pipe end rearwardly 31. In the method of forming straight tubular blanks into elbows, the steps comprising:

(a) cutting a blank so that the outer portion of each end is flat and the inner portion of each end is angularly tapered relative to the centerline of the blank, with the angle of taper on the trailing end being smaller than the anle of taper on the leading end thereof,

(b) positioning a path,

(c) placing the leading end portion of said blank over a mandrel,

(d) and moving said blank and said mandrel in fixed relation around said curved path by pressing initially on the at portion of the trailing end of the blank and subsequently progressively pressing on the tapered portion of the said trailing end.

32. The method of claim 31 which includes the step of holding the said outerwall of said blank under compression simultaneously with the said moving of the blank in a'curved pat 33. In a method of forming straight tubular blanks into elbows, the steps comprising:

(a) providing a hollow blank curved path,

(b) positioning a ymandrel forwardly of vthe forward end portion of said hollow blank,

(c) positioning the said forward end blank over said mandrel,

(d) and moving relation around said curved path by pressing on the trailing end of the blank while longitudinally conining the outer Wall of the blank.

34. In a method of forming straight tubular blanks into elbows, the steps comprising:`

(a) providing a blank for movement in a curved path,

(b) positioning a mandrel forwardly of the forward end portion of said blank,

(c) positioning the said forward end portion of said blank over said mandrel,

(d) moving said blank .and said mandrel lation around said curved path by pressing on trailing end of the blank,

(e) andv continuously holding the outer wall of said blank under lengthwise compression simultaneously with the said moving lof the blank in a curved path.

35. The method of claim 34 which includes the step `of maintaining the inner Wall of said blank in a condiblank for movement in a curved for movement in a portion of said in fixed rethe tion unconfined longitudinally simultaneous with said moving.

36. In a method for forming straight tubular blanks into curved elbows, the steps comprising:

(a) providing a pair of blanks for movement in succession in a curved path,

(b) positioning the leading end portion of an elongated mandrel land the trailing end portion of the first blank so that the mandrel is disposed within said rst blank,

(c) positioning the trailing end portion of said mandrel and the forward end portion of the second blank so that the mandrel is disposed within said second blank,

(d) and moving said blanks and said mandrel in fixed relation around said curved path by ypressing on tne 6 trailing end -of the said second blank. 37. In a method of forming straight into elbows, the steps comprising:

tubular blanks said blank and said mandrel in xed (a) providing a blank for movement in a curved path,

(b) positioning a mandrel having a generally bananashaped compound curved outer surface conforming to the outer wa ly of the forwar (c) positioning th blank over said (d) moving sai relation aroun trailing end of (e) and permitting movement o compound outer piece desired forwardend portion of said mandrel in fixed by pressing on the said mandrel to rock during curved f the blank and mandrel so that said surface Iprogressively supports against flattening the outer wall `of said blank from the forward end of the blank rearwardly toward the midportion thereof.

3S. In a method for into elbows, the steps (a) positioning a path, (b) and while simult the blank agai forward end o forming straight tubular blanks comprising: blank for movement in a 'curved moving said blank around said curved path aneously supporting the outer wall of nstflattening progressively from the fthe blank rearwardly to about the midportion thereof. 39. 'The method of claim 38 which includes the step of supporting the 4forward end of the inner wall of said blank against co llapse simultaneously with said `moving of the blank in a curved path.

40. In a method for eps comprising: blank for movement in a curved path, the leading end portion of said blank drel member,

into elbows, the st (a) providing a (b) positioning over a first man (c) positionin over a secon bers in fixe pressing on the mandrel members.

CHARLES W. LANHAM, Primary longitudinally confining 41. 'The method of claim of yieldingly resisting forming straight tubular blanks g the trailing end portion of said blank d mandrel member,

(d) and moving said blank and said d relation around said curved path by mandrel memtrailing end of said blank `while the `outer wall of the blank. 40 which includes the step the movement of said blank and References Cited by the Examiner UNlTED STATES PATENTS 4/1933 Brown 72-369 lO/l934 Flodin 29l57 3/1935 Cornell 72-133 5/1935 Cornell 29-157 ll/ 194() Taylor 72--209 1l/l943 Kvarnstrom 72-166 8/1944 Johnson 72--154 l/l952 Wyrfel 72--11 l0/l959 Armstrong et al 29-157 12/1959 Klein 72-166 2/1961 Armstrong et al 72-42 ll/l963 Stalter 72-166 FOREIGN PATENTS 7/ 1928 Germany.

Examiner.

R. D, GREFE, Assistant Examiner. 

30. IN A METHOD FOR FORMING LENGTHS OF METAL PIPE INTO ELBOWS, THE STEPS OF CUTTING THE ENDS OF A LENGTH OF PIPE TO PROVIDE AT THE OUTER RADIUS OF THE ELBOW END SURFACES PERPENDICULAR TO THE PIPE CENTERLINE AND AN END SURFACE INCLINED AT AN ACUTE ANGLE TO THE PIPE CENTERLINE, THE CUTTING BEING SUCH THAT THE AREAS OF INCLINED END SURFACES ARE GREATER AT THE TRAILING END OF THE PIPE THAN AT THE LEADING END THEREOF TO PROVIDE FOR FLOW OF A GREATER AMOUNT OF METAL TOWARD THE TRAILING PIPE END DURING FORMING, INSERTING THE PIPE INTO A CYLINDRICAL PASSAGE HAVING A CURVE WITH AN INNER AND AN OUTER RADIUS DEPENDENT ON THE DIMENSIONS OF THE LENGTH OF PIPE, PLACING THE LEADING END OF THE PIPE OVER A MANDREL ADAPTED TO TRAVELING WITH THE PIPE AROUND THE CURVE OF THE PASSAGE, AND PRESSING ON THE TRAILING PERPENDICULAR END SURFACE OF THE PIPE FOR FORCING THE PIPE AND THE MANDREL AROUND THE CURVE OF THE PASSAGE WHILE SUPPORTING THE OUTER PIPE WALL PROGRESSIVELY FROM THE FORWARD PIPE END REARWARDLY TOWARD THE PIPE MIDPORTION. 